When we materialize modify/delete conflicts, we currently don't
include any context lines. That's because modify/delete conflicts have
only two sides, so there's no common base to compare to. Hunks that
are unchanged on the "modify" side are therefore not considered
conflicting, and since they they don't contribute new changes, they're
simply skipped (here:
3dfedf5814/lib/src/files.rs (L228-L230)).
It seems more useful to instead pretend that the missing side is an
empty file. That way we'll get a conflict in the entire file.
We can still decide later to make e.g. `jj resolve` prompt the user on
modify/delete conflicts just like `hg resolve` does (or maybe it
actually happens earlier there, I don't remember).
Closes#1244.
e48ace56d1